This invention relates to the installation of photovoltaic modules directly to roof framing members, bypassing the construction and installation of separate rack superstructures.
There has existed for many years now, in the field of photovoltaic generation of electricity, a need for a simple, inexpensive, reliable method of attaching photovoltaic modules directly to roof framing members. In spite of continual predictions that this would soon be common practice, it has not become so. Instead the most common practice in roof mounting of photovoltaic modules has been to design, drill and bolt up angle iron into a rack to accept whatever size module has been purchased. Then to penetrate the roof covering in locations where framing members underlie the roof sheathing, to lag screw or preferably bolt the rack through frame members. The present methods of mounting photovoltaic modules onto roofs is somewhat expensive and very time consuming, at least when compared to the expense of, and time required to drive three roofing nails per module; and the present methods are prone to leaks at the roof covering penetrations
Photovoltaic modules, to operate efficiently, must be provided with good air circulation front and back, because about 90% to 95% of the light absorbed is converted to heat, not electricity, and, as the temperature rises, the electricity production reduces rapidly. People who do not realize how severe the effect is sometimes attach the modules directly to the roofing materials and in addition to exposure to leakage of water through the roof, suffer poor electrical production, and rapid degradation of the roofing materials.
An additional problem that had to be addressed in photovoltaic module installations has been that of providing sufficiently weatherproof electrical connections to minimize corrosion and degradation of the connection which has been a more serious problem in low voltage direct current wiring than in high voltage alternating current wiring.
From time to time attempts have been made to secure existing modules directly to roof framing members or to special added support members by adopting methods used in glazing sun space roofs. These methods eliminate the labor and materials of the fabrication and installation of special racks and the labor and materials needed to sheath and shingle a roof. Unfortunately, like sunspaces, unless very carefully engineered with expensive materials and installed with great care by skilled technicians, there is a high probability and in fact, near certainty that joints between modules will develope leaks. The continual expansion and contraction of the modules, as with glass and plastic glazing materials, is almost certain to open up any caulking or sealing method except for the very best and most carefully applied installations. Accepted standard framing practices assure that roof framing members will not be precisely enough positioned to permit standardized cap and sealing strip pieces to adequately seal the edges of heretofore manufactured photovolatic module frames.
Therefore it is the primary object of this invention to provide for the first time for the fastening of photovoltaic modules to ordinarily well installed roof framing with built in tolerance for normal variations.
Another object of this invention is to provide for installation of photovoltaic to nonstandard or substandard framing by adding common purlins.
Another object of this invention is to provide a tolerance for differential movement between framing members, between photovotaic modules, and between members and modules, caused by hot/cold cycling and by damp/dry cycling.
A further object of this invention is to provide a module installation which reduces the high labor and material costs associated with previous panel installations. Photovoltaic modules with the new flanges on their frames can be installed by any one who can carry a pocket full of nails and aim a hammer reasonably well. No more draping power cords onto the roof, no more drills, socket wrench sets, etc. No more guessing at the location of framing members. No more patching holes in roof coverings when the frame member is missed.
Another object of this invention is to reduce the expense and difficulty of making the electrical connections and of the wiring itself. Connection methods and wire suitable to interiors may be used instead of connections, methods and wire required to weatherproof exterior work.
Another object of this invention is to permit easy electrical isolation, and checking of individual modules. Access to the electrical connections is possible in any weather.
Another object of this invention is to permit easy removal and replacement of individual modules. This can be accomplished from either the top or from under the modules using ordinary hand tools.
An additional object of this invention is to permit installation of photovoltaic modules to virtually any properly pitched roof in which the framing members pretend to be in a single plane, even when the spacing of the members is not standard, by the addition of purlins on standard spacing.
Another object of this invention is to eliminate the expense and inherent problem of specially constructed roof racks.
Another object of this invention is to eliminate the expensive and unreliable caulking and sealing methods previously employed in direct to framing member installations.
A still further object of this invention is to assure adequate ventilation of both sides of the photovoltaic modules without the awkward and expensive methods previously employed.
Another object of this invention is to allow the use of standard readily available peak and eaves ventilating systems to cool the modules, or additional cooling air may be forced to flow past the underside of the modules by using standard gable or roof ventilating fans and controls, or the hot air may be used for interior heating purposes rather than being dumped directly outside.
Achievment of the objects of the invention is enabled through the addition of a specially formed set of flanges to a common photovoltaic module frame extrusion. The specially formed flanges eliminate the need to caulk or seal against the passage of water by inclusion of antiwicking grooves and drainage channels.